1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
4 *
5 * Authors:
6 * Serge Semin <Sergey.Semin@baikalelectronics.ru>
7 *
8 * Baikal-T1 Physically Mapped Internal ROM driver
9 */
10 #include <linux/bits.h>
11 #include <linux/device.h>
12 #include <linux/kernel.h>
13 #include <linux/mtd/map.h>
14 #include <linux/mtd/xip.h>
15 #include <linux/mux/consumer.h>
16 #include <linux/of.h>
17 #include <linux/of_device.h>
18 #include <linux/platform_device.h>
19 #include <linux/string.h>
20 #include <linux/types.h>
21
22 #include "physmap-bt1-rom.h"
23
24 /*
25 * Baikal-T1 SoC ROMs are only accessible by the dword-aligned instructions.
26 * We have to take this into account when implementing the data read-methods.
27 * Note there is no need in bothering with endianness, since both Baikal-T1
28 * CPU and MMIO are LE.
29 */
bt1_rom_map_read(struct map_info * map,unsigned long ofs)30 static map_word __xipram bt1_rom_map_read(struct map_info *map,
31 unsigned long ofs)
32 {
33 void __iomem *src = map->virt + ofs;
34 unsigned int shift;
35 map_word ret;
36 u32 data;
37
38 /* Read data within offset dword. */
39 shift = (uintptr_t)src & 0x3;
40 data = readl_relaxed(src - shift);
41 if (!shift) {
42 ret.x[0] = data;
43 return ret;
44 }
45 ret.x[0] = data >> (shift * BITS_PER_BYTE);
46
47 /* Read data from the next dword. */
48 shift = 4 - shift;
49 if (ofs + shift >= map->size)
50 return ret;
51
52 data = readl_relaxed(src + shift);
53 ret.x[0] |= data << (shift * BITS_PER_BYTE);
54
55 return ret;
56 }
57
bt1_rom_map_copy_from(struct map_info * map,void * to,unsigned long from,ssize_t len)58 static void __xipram bt1_rom_map_copy_from(struct map_info *map,
59 void *to, unsigned long from,
60 ssize_t len)
61 {
62 void __iomem *src = map->virt + from;
63 unsigned int shift, chunk;
64 u32 data;
65
66 if (len <= 0 || from >= map->size)
67 return;
68
69 /* Make sure we don't go over the map limit. */
70 len = min_t(ssize_t, map->size - from, len);
71
72 /*
73 * Since requested data size can be pretty big we have to implement
74 * the copy procedure as optimal as possible. That's why it's split
75 * up into the next three stages: unaligned head, aligned body,
76 * unaligned tail.
77 */
78 shift = (uintptr_t)src & 0x3;
79 if (shift) {
80 chunk = min_t(ssize_t, 4 - shift, len);
81 data = readl_relaxed(src - shift);
82 memcpy(to, (char *)&data + shift, chunk);
83 src += chunk;
84 to += chunk;
85 len -= chunk;
86 }
87
88 while (len >= 4) {
89 data = readl_relaxed(src);
90 memcpy(to, &data, 4);
91 src += 4;
92 to += 4;
93 len -= 4;
94 }
95
96 if (len) {
97 data = readl_relaxed(src);
98 memcpy(to, &data, len);
99 }
100 }
101
of_flash_probe_bt1_rom(struct platform_device * pdev,struct device_node * np,struct map_info * map)102 int of_flash_probe_bt1_rom(struct platform_device *pdev,
103 struct device_node *np,
104 struct map_info *map)
105 {
106 struct device *dev = &pdev->dev;
107
108 /* It's supposed to be read-only MTD. */
109 if (!of_device_is_compatible(np, "mtd-rom")) {
110 dev_info(dev, "No mtd-rom compatible string\n");
111 return 0;
112 }
113
114 /* Multiplatform guard. */
115 if (!of_device_is_compatible(np, "baikal,bt1-int-rom"))
116 return 0;
117
118 /* Sanity check the device parameters retrieved from DTB. */
119 if (map->bankwidth != 4)
120 dev_warn(dev, "Bank width is supposed to be 32 bits wide\n");
121
122 map->read = bt1_rom_map_read;
123 map->copy_from = bt1_rom_map_copy_from;
124
125 return 0;
126 }
127
